Fluid-dispensing chip

ABSTRACT

A fluid-dispensing chip has a wafer substrate that incorporates drive circuitry. A nozzle assembly is positioned on the wafer substrate. The nozzle assembly has nozzle chamber walls and a roof wall that define a nozzle chamber and a fluid ejection port in the roof wall and an electrostatic actuator. The actuator has a first planar electrode positioned on the wafer substrate. A second planar electrode is positioned in the nozzle chamber and is displaceable towards and away from the first planar electrode to eject fluid from the fluid ejection port. The first planar electrode and the second planar electrode are connected to the drive circuitry so that a potential difference can be applied between the planar electrodes to displace the second planar electrode towards and away from the first planar electrode. At least one of the nozzle chamber walls and the wafer substrate define a fluid inlet in fluid communication with the nozzle chamber and a fluid supply source.

Continuation-in part of prior application Ser. No. 09/113,070, filed Jul. 10, 1998, now U.S. Pat. No. 6,476,863.

CROSS REFERENCES TO RELATED APPLICATIONS

The following Australian provisional patent applications are hereby incorporated by cross-reference. For the purposes of location and identification, US patent applications identified by their US patent application serial numbers (USSN) are listed alongside the Australian applications from which the US patent applications claim the right of priority.

US Patent Application Cross-Referenced (Claiming Right of Priority Australian from Australian Provisional Patent No. Provisional Application) Docket No. PO7991 09/113,060 ART01 PO8505 09/113,070 ART02 PO7988 09/113,073 ARTO3 PO9395 09/112,748 ART04 PO8017 09/112,747 ART06 PO8014 09/112,776 ART07 PO8025 09/112,750 ART08 PO8032 09/112,746 ART09 PO7999 09/112,743 ART10 PO7998 09/112,742 ART11 PO8031 09/112,741 ART12 PO8030 09/112,740 ART13 PO7997 09/112,739 ART15 PO7979 09/113,053 ART16 PO8015 09/112,738 ART17 PO7978 09/113,067 ART18 PO7982 09/113,063 ART19 PO7989 09/113,069 ART20 PO8019 09/112,744 ART21 PO7980 09/113,058 ART22 PO8018 09/112,777 ART24 PO7938 09/113,224 ART25 PO8016 09/112,804 ART26 PO8024 09/112,805 ART27 PO7940 09/113,072 ART28 PO7939 09/112,785 ART29 PO8501 09/112,797 ART30 PO8500 09/112,796 ART31 PO7987 09/113,071 ART32 PO8022 09/112,824 ART33 PO8497 09/113,090 ART34 PO8020 09/112,823 ART38 PO8023 09/113,222 ART39 PO8504 09/112,786 ART42 PO8000 09/113,051 ART43 PO7977 09/112,782 ART44 PO7934 09/113,056 ART45 PO799O 09/113,059 ART46 PO8499 09/113,091 ART47 PO8502 09/112,753 ART48 PO7981 09/113,055 ART50 PO7986 09/113,057 ART51 PO7983 09/113,054 ART52 PO8026 09/112,752 ART53 PO8027 09/112,759 ART54 PO8028 09/112,757 ART56 PO9394 09/112,758 ART57 PO9396 09/113,107 ART58 PO9397 09/112,829 ART59 PO9398 09/112,792 ART60 PO9399 09/112,791 ART61 PO9400 09/112,790 ART62 PO9401 09/112,789 ART63 PO9402 09/112,788 ART64 PO9403 09/112,795 ART65 PO9405 09/112,749 ART66 PPO959 09/112,784 ART68 PP1397 09/112,783 ART69 PP2370 09/112,781 DOT01 PP2371 09/113,052 DOT02 PO8003 09/112,834 Fluid01 PO8005 09/113,103 Fluid02 PO9404 09/113,101 Fluid03 PO8066 09/112,751 IJ01 PO8072 09/112,787 IJ02 PO8040 09/112,802 IJ03 PO8071 09/112,803 IJ04 PO8047 09/113,097 IJ05 PO8035 09/113,099 IJ06 PO8044 09/113,084 IJ07 PO8063 09/113,066 IJ08 PO8057 09/112,778 IJ09 PO8056 09/112,779 IJ10 PO8069 09/113,077 IJ11 PO8049 09/113,061 IJ12 PO8036 09/112,818 IJ13 PO8048 09/112,816 IJ14 PO8070 09/112,772 IJ15 PO8067 09/112,819 IJ16 PO8001 09/112,815 IJ17 PO8038 09/113,096 IJ18 PO8033 09/113,068 IJ19 PO8002 09/113,095 IJ20 PO8068 09/112,808 IJ21 PO8062 09/112,809 IJ22 PO8034 09/112,780 IJ23 PO8039 09/113,083 IJ24 PO8041 09/113,121 IJ25 PO8004 09/113,122 IJ26 PO8037 09/112,793 IJ27 PO8043 09/112,794 IJ28 PO8042 09/113,128 IJ29 PO8064 09/113,127 IJ30 PO9389 09/112,756 IJ31 PO9391 09/112,755 IJ32 PP0888 09/112,754 IJ33 PP0891 09/112,811 IJ34 PP0890 09/112,812 IJ35 PP0873 09/112,813 IJ36 PP0993 09/112,814 IJ37 PP0890 09/112,764 IJ38 PP1398 09/112,765 IJ39 PP2592 09/112,767 IJ40 PP2593 09/112,768 IJ41 PP3991 09/112,807 IJ42 PP3987 09/112,806 IJ43 PP3985 09/112,820 IJ44 PP3983 09/112,821 IJ45 PO7935 09/112,822 IJM01 PO7936 09/112,825 IJM02 PO7937 09/112,826 IJM03 PO8061 09/112,827 IJM04 PO8054 09/112,828 IJM05 PO8065 09/113,111 IJM06 PO8055 09/113,108 IJM07 PO8053 09/113,109 IJM08 PO8078 09/113,123 IJM09 PO7933 09/113,114 IJM10 PO7950 09/113,115 IJM11 PO7949 09/113,129 IJM12 PO8060 09/113,124 IJM13 PO8059 09/113,125 IJM14 PO8073 09/113,126 IJM15 PO8076 09/113,119 IJM16 PO8075 09/113,120 IJM17 PO8079 09/113,221 IJM18 PO8050 09/113,116 IJM19 PO8052 09/113,118 IJM20 PO7948 09/113,117 IJM21 PO7951 09/113,113 IJM22 PO8074 09/113,130 IJM23 PO7941 09/113,110 IJM24 PO8077 09/113,112 IJM25 PO8058 09/113,087 IJM26 PO8051 09/113,074 IJM27 PO8045 09/113,089 IJM28 PO7952 09/113,088 IJM29 PO8046 09/112,771 IJM30 PO9390 09/112,769 IJM31 PO9392 09/112,770 IJM32 PP0889 09/112,798 IJM35 PP0887 09/112,801 IJM36 PP0882 09/112,800 IJM37 PP0874 09/112,799 IJM38 PP1396 09/113,098 IJM39 PP3989 09/112,833 IJM40 PP2591 09/112,832 IJM41 PP3990 09/112,831 IJM42 PP3986 09/112,830 IJM43 PP3984 09/112,836 IJM44 PP3982 09/112,835 IJM45 PP0895 09/113,102 IR01 PP0870 09/113,106 IR02 PP0869 09/113,105 IR04 PP0887 09/113,104 IR05 PP0885 09/112,810 IR06 PP0884 09/112,766 IR10 PP0886 09/113,085 IR12 PP0871 09/113,086 IR13 PP0876 09/113,094 IR14 PP0877 09/112,760 IR16 PP0878 09/112,773 IR17 PP0879 09/112,774 IR18 PP0883 09/112,775 IR19 PP0880 09/112,745 IR20 PP0881 09/113,092 IR21 PO8006 09/113,100 MEMS02 PO8007 09/113,093 MEMS03 PO8008 09/113,062 MEMS04 PO8010 09/113,064 MEMS05 PO8011 09/113,082 MEMS06 PO7947 09/113,081 MEMS07 PO7944 09/113,080 MEMS09 PO7946 09/113,079 MEMS10 PO9393 09/113,065 MEMS11 PP0875 09/113,078 MEMS12 PP0894 09/113,075 MEMS13

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE INVENTION

The present invention relates to fluid dispensing. In particular, this invention discloses a fluid-dispensing chip.

BACKGROUND OF THE INVENTION

This invention is a development of a printing technology that has been developed by the Applicant. This development can be traced by considering the referenced patents/patent applications set out above.

Many different types of printing have been invented, a large number of which are presently in use. The known forms of printing have a variety of methods for marking the print media with a relevant marking media. Commonly used forms of printing include offset printing, laser printing and copying devices, dot matrix type impact printers, thermal paper printers, film recorders, thermal wax printers, dye sublimation printers and ink jet printers both of the drop on demand and continuous flow type. Each type of printer has its own advantages and problems when considering cost, speed, quality, reliability, simplicity of construction and operation etc.

In recent years, the field of ink jet printing, wherein each individual pixel of ink is derived from one or more ink nozzles has become increasingly popular primarily due to its inexpensive and versatile nature.

Many different techniques of ink jet printing have been invented. For a survey of the field, reference is made to an article by J Moore, “Non-Impact Printing: Introduction and Historical Perspective”, Output Hard Copy Devices, Editors R Dubeck and S Sherr, pages 207-220 (1988).

Ink Jet printers themselves come in many different types. The utilisation of a continuous stream of ink in ink jet printing appears to date back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hansell discloses a simple form of continuous stream electro-static ink jet printing.

U.S. Pat. No. 3,596,275 by Sweet also discloses a process of continuous ink jet printing including the step wherein the ink jet stream is modulated by a high frequency electro-static field so as to cause drop separation. This technique is still utilized by several manufacturers including Elmjet and Scitex (see also U.S. Pat. No. 3,373,437 by Sweet et al)

Piezoelectric ink jet printers are also one form of commonly utilized ink jet printing device. Piezoelectric systems are disclosed by Kyser et al. in U.S. Pat. No. 3,946,398 (1970) which utilises a diaphragm mode of operation, by Zolten in U.S. Pat. No. 3,683,212 (1970) which discloses a squeeze mode of operation of a piezoelectric crystal, Stemme in U.S. Pat. No. 3,747,120 (1972) discloses a bend mode of piezo-electric operation, Howkins in U.S. Pat. No. 4,459,601 discloses a Piezoelectric push mode actuation of the ink jet stream and Fischbeck in U.S. Pat. No. 4,584,590 which discloses a sheer mode type of piezoelectric transducer element.

Recently, thermal ink jet printing has become an extremely popular form of ink jet printing. The ink jet printing techniques include those disclosed by Endo et al in GB 2007162 (1979) and Vaught et al in U.S. Pat. No. 4,490,728. Both the aforementioned references disclosed ink jet printing techniques rely upon the activation of an electrothermal actuator which results in the creation of a bubble in a constricted space, such as a nozzle, which thereby causes the ejection of ink from an aperture connected to the confined space onto a relevant print media. Manufacturers such as Canon and Hewlett Packard manufacture printing devices utilising the electro-thermal actuator.

As can be seen in the above referenced matters, Applicant has developed an ink jet printing technology that uses micro-electromechanical components to achieve the ejection of ink. The use of micro-electromechanical components allows printhead chips to have a large number of densely packed nozzle arrangements without the problems associated with heat build-up.

Applicant envisages that this technology can be used to dispense fluid. This invention is therefore intended to be a simple development of the technology that has already been the subject of many patent applications filed by the Applicant.

SUMMARY OF THE INVENTION

According to the invention, there is provided a fluid-dispensing chip that comprises

a wafer substrate that incorporates drive circuitry, and

a nozzle assembly positioned on the wafer substrate, the nozzle assembly comprising

nozzle chamber walls and a roof wall that define a nozzle chamber and a fluid ejection port in the roof wall, and

an electrostatic actuator that comprises

a first planar electrode positioned on the wafer substrate, and

a second planar electrode that is positioned in the nozzle chamber and is displaceable towards and away from the first planar electrode to eject fluid from the fluid ejection port, the first planar electrode and the second planar electrode being connected to the drive circuitry so that a potential difference can be applied between the planar electrodes to displace the second planar electrode towards and away from the first planar electrode,

at least one of the nozzle chamber walls and the wafer substrate defining a fluid inlet in fluid communication with the nozzle chamber and a fluid supply source, said first planar electrode and said second planar electrode defining an air gap between the first and second planar electrodes.

At least one of the nozzle chamber walls and the substrate may define an air path in fluid communication with an external atmosphere so that air flows into and out of the air gap when the second planar electrode is displaced towards and away from the first planar electrode.

The electrodes may have facing surfaces that are coated with a material having a low coefficient of friction to reduce possibilities of stiction. Said material may comprise substantially polytetrafluoroethylene.

Instead, or in addition, one of the first and second planar electrodes may have at least one projection that extends towards the other electrode to ensure that the electrodes do not touch when the second planar electrode is displaced towards the first planar electrode.

Said second planar electrode may include a layer of stiffening material for maintaining a stiffness of the second planar electrode. The stiffening material may be silicon nitride.

The roof wall may define a plurality of etchant holes to facilitate etching of sacrificial layers during construction.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of the present invention, preferred forms of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is a sectioned side view of one embodiment of a fluid-dispensing chip of the invention, in an operative condition.

FIG. 2 is a sectioned side view of the fluid-dispensing chip of FIG. 1 in a quiescent condition.

FIG. 3 is a perspective cross-sectional view of another embodiment of the fluid-dispensing chip of the invention.

FIG. 4 is a close-up perspective cross-sectional view (portion A of FIG. 3), of the fluid-dispensing chip of FIG. 3.

FIG. 5 is an exploded perspective view illustrating the construction of the fluid-dispensing chip of FIG. 3.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

In FIGS. 1 and 2, reference numeral 10 generally indicates a sectioned side view of one embodiment of a fluid-dispensing chip of the invention.

The fluid-dispensing chip may include a silicon wafer substrate 12. A drive circuitry layer 14 is positioned on the wafer substrate 12. The drive circuitry layer 14 is in the form of a CMOS two-level metal layer that includes the drive and control circuitry for the fluid-dispensing chip 10.

A passivation layer 16 of silicon nitride is positioned on the drive circuitry layer 14 to protect the drive circuitry layer 14. A first planar electrode 18 is embedded in the layer 16. The first planar electrode 18 is of aluminum and is connected to the drive circuitry layer 14.

The fluid-dispensing chip 10 includes a nozzle chamber wall 19 and a roof wall 20 that define a nozzle chamber 22. The roof wall 20 defines a fluid ejection port 44. A fluid-ejecting member 28 is positioned in the nozzle chamber 22. The fluid-ejecting member 28 is planar and is aligned with and parallel to the first planar electrode 18.

The fluid-ejecting member 28 is positioned on a support formation 34 that extends from the passivation layer 16. The support formation 34 is dimensioned so that the fluid-ejecting member 28 is spaced a suitable distance from the first electrode 18. The support formation 34 is configured so that an air gap 40 is encapsulated between the fluid-ejecting member 28 and the first electrode 18.

The fluid-ejecting member 28 includes a second planar electrode 24 that is positioned in the nozzle chamber 22. The second planar electrode 24 is also of aluminum and is also connected to the drive circuitry layer 14. The drive circuitry layer 14 is connected to each of the electrodes 18, 24 so that a potential can be set up between the electrodes 18, 24 so that they are attracted to one another. A layer 26 of silicon nitride is positioned on the electrode 24 to impart a resilient flexibility to the fluid-ejecting member 28. Thus, when a potential is set up between the electrodes 18, 24, the fluid-ejecting member 28 is deflected towards the first electrode 18, as shown in FIG. 1. When the potential is removed, the first electrode 18 returns to a quiescent position as shown in FIG. 2.

A layer 32 of polytetrafluoroethylene (PTFE) is positioned on the first electrode 18. A layer 36 of PTFE is positioned on the second electrode 24, intermediate the electrodes 18, 24. This ensures that the electrodes 18, 24 do not stick to one another when the fluid-ejecting member 28 is deflected towards the first electrode 18. In order further to prevent stiction between the electrodes 18, 24, a projection 38 is positioned on the fluid-ejecting member 28. The projection 38 bears against the layer 32 to ensure that there is no contact between the layers 32, 36.

The nozzle chamber wall 19 defines fluid inlet openings 30 that are in fluid communication with a fluid supply so that the nozzle chamber 22 can be supplied with fluid. Fluid flows into a space 41 defined by the roof wall 20, the nozzle chamber wall 19, the fluid-ejecting member 28 and the support formation 34. It will be appreciated that this occurs when the fluid-ejecting member 28 is drawn towards the first electrode 18. When the potential is reversed, the fluid-ejecting member 28 is urged away from the first electrode 18 so that a drop 42 of fluid is ejected from the fluid ejection port 44. The fluid-ejecting member 28 could have sufficient resilience so that a reversal of potential is not necessary. In this case, release of elastic energy as the fluid-ejecting member 28 returns to its quiescent condition ensures the ejection of the fluid drop 42.

The roof wall 20 defines a rim 46 about the fluid ejection port 44.

In FIGS. 3 to 5, reference numeral 50 generally indicates another embodiment of a fluid-dispensing chip of the invention. With reference to FIGS. 1 and 2, like reference numerals refer to like parts, unless otherwise specified.

The fluid-ejecting member 28 has a peripheral portion 52 that is positioned between the nozzle chamber wall 19 and the layer 26 of silicon nitride. A corrugated annular portion 54 is positioned adjacent to the peripheral portion 52. A fluid-ejecting portion 56 defines a remainder of the fluid-ejecting member 28.

The electrodes 18, 24 and their respective PTFE layers 32, 36 are dimensioned to define the air gap 40.

The corrugated portion 54 is configured to expand when the second electrode 24 is displaced towards the first electrode 18. The silicon nitride layer 26 imparts a resilient flexibility to the corrugated portion 54. Thus, the second electrode 24 returns to a quiescent condition when the electrical potential is removed.

The nozzle chamber wall 19 is shaped to define four radially spaced fluid inlet supply channels 58 that are in fluid communication with the space 41. These allow fluid to flow into the space 41 when the second electrode 24 is drawn towards the first electrode 18.

The nozzle chamber wall 19 defines air spaces 60 that are in fluid communication with the air gap 40. These allow the passage of air when the second electrode 24 moves towards and away from the first electrode 18.

The roof wall 20 has a plurality of etchant openings 62 defined therein to facilitate the etching of sacrificial material used in the fabrication of the chip 50. The etchant openings 62 are small enough to inhibit the passage of fluid as a result of surface tension effects.

It is important to note that the fluid-dispensing chip 10, 50 is essentially a micro-electromechanical systems (MEMS) device. A method for fabricating the device can readily be deduced from the description in referenced application no: U.S. Pat. No. 09/112,787 and in many of the other referenced applications.

Applicant envisages that the fluid-dispensing chip 10, 50 will be particularly suited for lab-on-a-chip applications. It can also be applied to DNA/RNA arrays, protein chips and sensing and dosing. The fluid-dispensing chip 10, 50 could also be used for drug delivery systems.

Numerous variations and/or modifications may be made to the present invention as shown in the preferred embodiment without departing from the spirit or scope of the invention as broadly described. The preferred embodiment is, therefore, to be considered in all respects to be illustrative and not restrictive. 

What is claimed is:
 1. A fluid-dispensing chip that comprises a wafer substrate that incorporates drive circuitry, and a nozzle assembly positioned on the wafer substrate, the nozzle assembly comprising nozzle chamber walls and a roof wall that define a nozzle chamber and a fluid ejection port in the roof wall, and an electrostatic actuator that comprises a first planar electrode positioned on the wafer substrate, and a second planar electrode that is positioned in the nozzle chamber and is displaceable towards and away from the first planar electrode to eject fluid from the fluid ejection port, the first planar electrode and the second planar electrode being connected to the drive circuitry so that a potential difference can be applied between the planar electrodes to displace the second planar electrode towards and away from the first planar electrode, at least one of the nozzle chamber walls and the wafer substrate defining a fluid inlet in fluid communication with the nozzle chamber and a fluid supply source, said first planar electrode and said second planar electrode defining an air gap between the first and second planar electrodes.
 2. A fluid-dispensing chip as claimed in claim 1, in which at least one of the nozzle chamber walls and the substrate define an air path in fluid communication with an external atmosphere so that air flows into and out of the air gap when the second planar electrode is displaced towards and away from the first planar electrode.
 3. A fluid-dispensing chip as claimed in claim 1, wherein the electrodes have facing surfaces that are coated with a material having a low coefficient of friction so as to reduce possibilities of stiction.
 4. A fluid-dispensing chip as claimed in claim 3, wherein said material comprises substantially polytetrafluoroethylene.
 5. A fluid-dispensing chip as claimed in claim 1, in which one of the first and second planar electrodes has at least one projection that extends towards the other electrode to ensure that the electrodes do not touch when the second planar electrode is displaced towards the first planar electrode.
 6. A fluid-dispensing chip as claimed in claim 1, wherein said second planar electrode includes a layer of stiffening material for maintaining a stiffness of said second planar electrode.
 7. A fluid-dispensing chip as claimed in claim 6, wherein said stiffening material is silicon nitride.
 8. A fluid-dispensing chip as claimed in claim 1, wherein the roof wall defines a plurality of etchant holes to facilitate etching of sacrificial layers during construction. 